Electromagnetically shielded video camera and shielded enclosure for image capture devices

ABSTRACT

Camera arrangements that can include electromagnetic protection, such as from EMP/IEMI events, is disclosed. One example camera arrangement includes a camera including a viewfinder having a lens, and an electromagnetically shielded enclosure defining an interior volume containing the camera and configured to include at least one opening aligned with the lens. The camera arrangement includes a waveguide beyond cutoff disposed across the at least one opening, the waveguide beyond cutoff including a plurality of cells sized and oriented to shield the interior volume of the enclosure from electromagnetic signals while exposing an optical path between the lens and objects external to the enclosure.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. Provisional Patent Application No. 61/410,755 filed on Nov. 5, 2010, the disclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to structures for protection of electronic devices from electromagnetic events. In particular, the present disclosure relates to an electromagnetically shielded video or infrared camera, and a shielded enclosure for image capture devices.

BACKGROUND

Exposure to electromagnetic fields can cause interference or damage to electrical equipment, causing that equipment to malfunction or rendering it nonoperational. For example, electrical equipment and electronics can be destroyed, or otherwise fail in the event of a strong electromagnetic pulse or intentional electromagnetic interference event (EMP/IEMI).

EMP/IEMI events typically take one of two forms. First, high field events correspond to short-duration, high voltage events (e.g., up to and exceeding 100 kilovolts per meter), and typically are of the form of short pulses of narrow-band or distributed signals (e.g., in the frequency range of 14 kHz to 10 GHz). These types of events typically generate high voltage differences in equipment, leading to high induced currents and burnout of electrical components. Second, low field events (e.g., events in the range of 0.01 to 10 volts per meter) are indications of changing electromagnetic environments below the high field damaging environments, but still of interest in certain applications.

Existing systems are used to adjust to a narrow range of threats, and thus systems developed to address a certain problem are not useful to address other problems necessitating electromagnetic shielding that are exposed during use of other electronic equipment. One such unaddressed concern is for example equipment related to surveillance, such as video and infrared cameras. Typically, video camera lenses require exposure to an external environment to provide a field of view for that camera to capture. In circumstances where reliable operation through possibly damaging events is desirable, such as in the case of security cameras or sensitive image capture equipment, there is currently no reliable way to ensure such operation in the case of exposure of the camera to possible damage due to EMP/IEMI events.

For these and other reasons, improvements are desirable.

SUMMARY

In accordance with the following disclosure, the above and other issues are addressed by the following:

In a first aspect, an electromagnetically protected camera arrangement includes a camera including a viewfinder having a lens. The camera arrangement also includes an electromagnetically shielded enclosure defining an interior volume containing the camera and configured to include at least one opening aligned with the lens. The camera arrangement also includes a waveguide beyond cutoff disposed across the at least one opening, the waveguide beyond cutoff including a plurality of cells sized and oriented to shield the interior volume of the enclosure from electromagnetic signals while exposing an optical path between the lens and objects external to the enclosure.

In a second aspect, a camera arrangement includes a video or infrared camera including a viewfinder having a lens, and an electromagnetically shielded enclosure defining an interior volume containing the video camera and configured to include at least one opening aligned with the lens. The camera arrangement also includes an electrical filter positioned along a surface of the electromagnetically shielded enclosure and configured to receive a power signal external to the electromagnetically shielded enclosure and pass a filtered power signal to the video camera. The camera arrangement further includes a waveguide beyond cutoff disposed across the at least one opening and at a distance from the lens less than a focal length of the lens, the waveguide beyond cutoff including a plurality of hexagonal or other shape cells sized and oriented to shield the interior volume of the enclosure from electromagnetic signals while exposing an optical path between the lens and objects external to the enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a schematic block diagram of an electromagnetically shielded camera, according to a possible embodiment;

FIG. 2 is a side cross-sectional schematic block diagram view of the electromagnetically shielded camera of FIG. 1;

FIG. 3 is a schematic front layout of a portion of a waveguide beyond cutoff useable to implement aspects of the present disclosure;

FIG. 4 is a schematic side layout of a portion of a waveguide beyond cutoff useable to implement aspects of the present disclosure; and

FIG. 5 is a schematic perspective view of a portion of a waveguide beyond cutoff useable to implement aspects of the present disclosure.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the claimed invention.

In general, the present disclosure relates to an electromagnetically shielded video camera and a shielded enclosure for image capture devices. In some embodiments disclosed herein, the shielded enclosure is configured to shield the camera from Electromagnetic Pulse or Intentional Electromagnetic Interference (EMP/IEMI) events. The electromagnetically shielded camera arrangements disclosed herein mitigate a risk of damage to optical equipment in the event of an electromagnetic event that would otherwise cause such damage. As such, electromagnetically shielded camera arrangements can be used in a variety of secure locations where monitoring is desired, such as in secure facilities (e.g., banks, utility buildings, government buildings, or other locations).

Referring now to FIGS. 1-2, an electromagnetically shielded camera 100 is shown, according to a possible embodiment of the present disclosure. FIG. 1 illustrates a front view of a schematic block diagram of the electromagnetically shielded camera 100, while FIG. 2 illustrates a side cross-sectional schematic view of that camera along an axis “A” depicted in FIG. 1.

In the embodiment shown, the electromagnetically shielded camera 100 includes a waveguide beyond cutoff 102 mounted in a wall of an enclosure 104.

Specifically, the arrangement 100 includes a waveguide 102, usually comprised of small, thin-walled conductive hexagonal or other shape cells 103, mounted in a wall of an enclosure 104 which encloses and shields a camera 106 and associated lens 108.

The waveguide beyond cutoff 102 can be, in various embodiments, constructed from metal or other materials, and is configured and positioned to allow optical communication between an internal area of the enclosure 104 and an area external to the enclosure, for example providing an optical path, or field of view, to a camera 106 and associated lens 108.

In general, the waveguide beyond cutoff 102 includes a honeycomb-shaped (i.e., hexagonal) or otherwise regularly-shaped geometric cells having a predetermined size and length, such that incident, high frequency signals external to the enclosure 104 are attenuated upon reaching the waveguide beyond cutoff 102. In certain embodiments, the waveguide 102 is a honeycomb structure and is designed such that it attenuates EMP and IEMI waves to a sufficient level (sometimes the level is 80 db with a frequency range from typically 14 kHz to as high as 10 GHz but other levels and other frequencies are obtainable to meet different levels of protection desired) so as to protect the electronics within the enclosure 104 and within the camera. It is understood that the waveguide 102 may be typically be made of one or more of the cells 103, such as honeycomb shaped hexagonal cells, round cells, square cells, vanes or other structures with small effective diameter and sufficient length through to provide the proper shielding. Usually, the air or in this case light passage is through the multiple openings in the waveguide 102 that are typically in the order of 1/16″ to ⅛″ in size. For optical use, the vanes defining the cells 103 should have a minimized thickness to minimize interference with optical paths passing through the waveguide beyond cutoff 102.

In the embodiment shown, the waveguide 102 is oriented in line with the light passing to the lens 108, so that the thin walls of the cells 103 provide minimal distortion, blockage or degradation of the image. The waveguide 102 is similar in principle to commercial waveguides designed to block entry of electromagnetic fields through air ducts used for cooling computers in shielded enclosures. Such waveguides are as described below. It is understood that other features of the enclosure must work in concert with the shielding of this light path to the lens 108 to provide complete, enclosed protection of the camera 106, including shielding of all necessary penetrations of the enclosure 104 from electromagnetic field penetration, interference or damage. Examples of a waveguide beyond cutoff useable in conjunction with the present disclosure are discussed below in connection with FIGS. 3-5.

The enclosure 104 is generally configured to be an electromagnetically-shielding enclosure, capable of shielding an interior volume 110 of the enclosure from undesirable electromagnetic signals (e.g., electromagnetic signals exceeding a particular amplitude and frequency). In various embodiments, the enclosure 104 can be constructed from conductive materials, such as a metal (e.g., sheet metal or aluminum) having a thickness generally sufficient to attenuate electromagnetic signals to acceptable levels. Although in the embodiment shown the enclosure 104 is generally rectangular, it is understood that the enclosure 104 could be any of a variety of shapes.

In an example embodiment, the enclosure 104 provides about 70 dB or more of attenuation. However, in alternative embodiments, other levels of attenuation could be provided as well. Various features relating to electromagnetically-shielding enclosures, as well as methods for sealing such enclosures, are provided in copending U.S. patent application Ser. No. 13/285,581, filed on Oct. 31, 2011, the disclosure of which is hereby incorporated by reference in its entirety.

In the embodiment shown, a frame 105 can be used to mount the waveguide beyond cutoff 102 to the enclosure 104. In various embodiments, the frame can provide a sealing connection to the enclosure 104, for example using an electromagnetically-shielded gasket arrangement or other arrangements, as explained in copending U.S. patent application Ser. No. 13/285,581, which was previously incorporated by reference.

As illustrated in further detail in FIG. 2, the camera 106 can be, in various embodiments, any of a variety of camera types, such as a still camera or video camera or infrared camera, and can be configured for use in various types of systems, such as security systems, closed-circuit monitoring systems, or other integrated systems. Alternatively, the camera 106 can be a stand-alone component, without a data connection external to the camera. In the embodiment shown, the camera 106 is powered by an external power signal line 112 which enters the enclosure 104 at an electrical filter 114. Various types of electrical filters could be used, such as a low-pass, band pass, or spark gap type filter; generally, the filter is selected to be capable of receiving a power signal (e.g., either a direct current signal having a predetermine voltage and amplitude, or an alternating current signal having an expected frequency and amplitude). The filter can be configured to prevent signals over a predetermined amplitude or frequency (e.g., within the range of typical EMP/IEMI events up to 10 GHz) from entering the enclosure via the power signal line 112.

The lens 108 can be any of a variety of types of automatically focusing or manually focused lenses. Generally, the lens 108 will have a focus length at a distance greater than the distance at which the waveguide beyond cutoff 102 is placed, such that the camera 106 does not focus on the waveguide, but instead focuses “through” the waveguide beyond cutoff on objects external to the enclosure 104. That is, the camera lens 108 can be selected, specific focal length and f-stop, such that the camera 106 focuses on objects in the far field. Hence the honeycomb waveguide material of the cells 103, which is in the near field, will be outside the depth of focus of the camera, and obscuration will be minimized. In this way, the imaging quality of the camera image will be retained with minimal distortion. In the embodiment shown, because the camera 106, lens 108 and waveguide 102 are mounted in alignment, viewing through the honeycomb waveguide cells 103 is nearly unobstructed.

In certain embodiments, an additional optical grade lens or window could optionally be located in “front” of the waveguide beyond cutoff 102 (external to the enclosure 104) to protect the camera and wave guide from exposure to environmental conditions.

Referring to FIGS. 3-5 example diagrams of the honeycomb waveguide beyond cutoff 102 are illustrated. In various embodiments, cells 103 forming the waveguide beyond cutoff 102 can be constructed of either aluminum or steel, or other types of electromagnetically conductive materials. The honeycomb structure of the waveguide beyond cutoff 102 typically has ⅛″ diameter (i.e., width) hexagonal holes forming an array of cells 103. To achieve the desired electromagnetic wave attenuation, typically 80 db, the thickness of the material (represented in FIG. 4 as length “X”) is typically on the order of one inch, but may vary in different embodiments. For a ⅛″ hole diameter this represents an length to diameter ratio of about eight (8). The honeycomb material of the waveguide beyond cutoff 102 can be plated or coated with a coating that is highly absorptive and non-reflective in the wavelengths of interest, to prevent unwanted off-axis light, or infrared, from entering the camera.

Referring generally to FIGS. 1-5, it can be seen that the shielded enclosure and waveguide beyond cutoff arrangement disclosed herein protect the path or opening for light to enter a shielded enclosure and then to enter the camera lens and image sensors without providing a leakage path for electromagnetic fields potentially harmful to the electrical and electronic systems of the camera to enter the enclosure.

The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. 

The invention claimed is:
 1. An electromagnetically protected camera arrangement comprising: a camera including a viewfinder having a lens; an electromagnetically shielded enclosure defining an interior volume containing the camera and configured to include at least one opening aligned with the lens; and a waveguide beyond cutoff disposed across the at least one opening, the waveguide beyond cutoff including a plurality of hexagonally-shaped cells sized and oriented to shield the interior volume of the enclosure from electromagnetic interference signals while exposing an optical path between the lens and objects external to the enclosure, wherein the waveguide beyond cutoff is placed in front of the lens at a distance less than a focal length of the lens.
 2. The electromagnetically protected camera arrangement of claim 1, wherein the camera comprises a video camera.
 3. The electromagnetically protected camera arrangement of claim 1, further comprising a power signal received into the interior volume of the enclosure at an electrical signal filter.
 4. The electromagnetically protected camera arrangement of claim 1, further comprising a frame mounting the waveguide beyond cutoff to the electromagnetically shielded enclosure.
 5. The electromagnetically protected camera arrangement of claim 1, wherein the cells of the waveguide beyond cutoff are one inch in length.
 6. The electromagnetically protected camera arrangement of claim 1, wherein the cells of the waveguide beyond cutoff are one eighth inches in width.
 7. The electromagnetically protected camera arrangement of claim 1, wherein the electromagnetically shielded enclosure comprises a metal enclosure.
 8. The electromagnetically protected camera arrangement of claim 1, wherein the electromagnetically shielded enclosure provides at least 70 dB of attenuation of the electromagnetic interference signals.
 9. The electromagnetically protected camera arrangement of claim 1, further comprising a second lens or window external to the enclosure and at least partially covering the waveguide beyond cutoff.
 10. The electromagnetically protected camera arrangement of claim 1, wherein the electromagnetic interference signals include intentional electromagnetic interference (IEMI).
 11. A camera arrangement comprising: a video, infrared or still camera including a viewfinder having a lens; an electromagnetically shielded enclosure defining an interior volume containing the video camera and configured to include at least one opening aligned with the lens; an electrical filter positioned along a surface of the electromagnetically shielded enclosure and configured to receive a power signal external to the electromagnetically shielded enclosure and pass a filtered power signal to the video camera; and a waveguide beyond cutoff disposed across the at least one opening and at a distance from the lens less than a focal length of the lens, the waveguide beyond cutoff including a plurality of hexagonal cells sized and oriented to shield the interior volume of the enclosure from electromagnetic interference signals while exposing an optical path between the lens and objects external to the enclosure.
 12. The camera arrangement of claim 11, wherein the waveguide beyond cutoff is coated with an antireflective material.
 13. The camera arrangement of claim 11, further comprising a frame mounting the waveguide beyond cutoff to the electromagnetically shielded enclosure.
 14. The camera arrangement of claim 11, further comprising a second lens external to the enclosure and at least partially covering the waveguide beyond cutoff.
 15. The camera arrangement of claim 11, wherein the electromagnetically shielded enclosure provides at least 70 dB of attenuation of the electromagnetic interference signals.
 16. The camera arrangement of claim 11, wherein the electromagnetic interference signals include intentional electromagnetic interference (IEMI). 